Golf club shaft and golf club

ABSTRACT

A golf club shaft has a function of attenuating the vibration of the shaft at the time of impact and also having a function of stabilizing the struck ball. A shaft has an inner bias layer having a fiber direction that was inclined with respect the shaft axial direction and an outer bias layer having a fiber direction that is inclined with respect to the shaft axial direction in a direction opposite from that of the inner bias layer laminated as a fiber-reinforced resin layer, and a vibration-damping material sheet layer having a vertical-direction length of about 110 mm to about 150 mm disposed between the inner bias layer and the outer bias layer, with region of the position of the end of the grip attachment location as the rear end in the vertical direction.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority on Japanese Patent Application No.2009-210469 filed Sep. 11, 2009, which is incorporated herein byreference in its entirety.

BACKGROUND OF THE INVENTION

The present invention relates to a golf club shaft that is formed usingfiber-reinforced resins, and to a golf club including the same, and moreparticularly, relates to a golf club shaft and a golf club using thesame that has improved vibration characteristics at the time of impactand stability of a ball that is struck.

Among conventional shafts made from a hollow tubular body as a shaft fora golf club with improved vibration characteristics at the time ofimpact, one has been proposed in which the hollow tubular body of theshaft is filled with a foam (Japanese Patent Application Publication No.6-182007).

Although when a player makes a shot that is off-center on the club head,the shaft vibrates irregularly and an unpleasant numbing sensationoccurs, because the hollow tubular body of the golf club shaft in theJapanese Patent is filled with a foam, the vibration characteristics ofthe foam cause a reduction in the irregular vibration of the shaft inthe case of an off-center impact, and thereby causes a reduction in theunpleasant numbing sensation.

However, although the golf club shaft of the Japanese Patent can reducethe irregular vibration of the shaft at the time of an off-center impactby the vibration-absorbing characteristics of the foam, it did not havea function that stabilizes the struck ball.

SUMMARY OF THE INVENTION

The present invention was made in view of the above circumstances, andthe present invention has as an object to provide a shaft for a golfclub and a golf club that have a shaft vibration-attenuating function atthe time of impact and a function of stabilizing a struck ball.

In order to achieve the above object, the present invention provides, asdescribed below, a first aspect of the invention of a shaft for a golfclub, and a second aspect and a third aspect of the invention of a golfclub.

The first aspect of the invention is a golf club shaft including aplurality of resin layers as the plurality of resin layers including aninner bias fiber-reinforced resin layer with reinforcing fibers alignedalong a first direction that is inclined with respect to the shaft axialdirection; an outer bias fiber-reinforced resin layer along a seconddirection is inclined with respect to the shaft axial direction oppositeto the first direction; and a vibration-damping material sheet layerhaving a vertical-direction length of about 110 mm to about 150 mm, ormore preferably from about 120 mm to about 140 mm, being interposedbetween the inner bias layer and the outer bias layer and beingpositioned at a range from about 55% to about 80% of the shaft length,or more preferably from about 56% to about 76%, from a shaft tip.

The second aspect of the invention is a golf club using a golf clubshaft including a plurality of resin layers as the plurality of resinlayers including an inner bias fiber-reinforced resin layer withreinforcing fibers aligned along a first direction that is inclined withrespect to the shaft axial direction; an outer bias fiber-reinforcedresin layer along a second direction is inclined with respect to theshaft axial direction opposite to the first direction; and avibration-damping material sheet layer having a vertical length of about110 mm to about 150 mm, or more preferably from about 120 mm to about130 mm, being interposed between the inner bias layer and the outer biaslayer, and being positioned from about 235 mm to about 270 mm, or morepreferably from about 245 mm to about 260 mm, from a butt end of theshaft taken as the rear end in the vertical direction.

The third aspect of the invention is a golf club using a golf club shaftincluding a plurality of layers as the plurality of resin layersincluding an inner bias fiber-reinforced resin layer with reinforcingfibers aligned along a first direction that is inclined with respect tothe shaft axial direction; an outer bias fiber-reinforced resin layerwith reinforcing fibers aligned along a second direction is inclinedwith respect to the shaft axial direction opposite to the firstdirection; and a vibration-damping material sheet layer having avertical length of about 110 mm to about 150 mm, or more preferably fromabout 120 mm to about 140 mm, being interposed between the inner biaslayer and the outer bias layer, and being positioned at a region of aposition of the end of the grip attachment location is taken as the rearend in the vertical direction.

Because the golf club shaft of the present invention basically has theregion of the position of the end of the grip attachment location as therear end in the vertical direction and a vibration-damping materialsheet with a vertical-direction length of about 110 mm to about 150 mm,the vibration-attenuating action of the vibration-damping material sheetreduces the vibration of the shaft at the time of impact and attenuatesthe vibration quickly, thereby improving the impact feel. The golf clubshaft of the present invention also has a low rigidity in the part inwhich the vibration-damping material sheet is disposed, and as a resultof the ease of flexure in the location in which the vibration-dampingmaterial sheet is disposed, the overall shaft flexes, making the shafteasy to swing and stabilizing the ball that is struck.

The present invention will now be described in further detail. The golfclub shaft according to the present invention has a plurality offiber-reinforced resin layers in which the reinforcing fibers arealigned in one direction. It is possible to use, for example, carbonfibers, glass fibers, metal fibers, aramid fibers, silicon carbidefibers, alumina fibers, and boron fibers as the above-noted reinforcingfibers. As a thermally cured resin of the reinforced fiber resin layer,it is possible to use an epoxy resin, a phenol resin, an unsaturatedpolyester resin or the like, or a combination of a plurality thereof.Additionally, it is possible to use a curing agent, a curingaccelerator, a filler, a parting agent, or a pigment, or the like as asupplemental substance.

The fiber-reinforced resin layer of the shaft according to the presentinvention can be formed, for example, by a sheet winding method ofwinding a prepreg sheet around a metal core (mandril) and subjectingthis to thermal curing. As the prepreg sheet, it is possible to use aroving, cloth, or mat that has been aligned in parallel and impregnatedin a thermally cured resin. The above-noted inner bias layer and outerbias layer are essential as fiber-reinforced resin layers in the presentinvention. The appropriate angle between the fiber direction of theinner bias layer and outer bias layer and the shaft axial direction isfrom about 35° to about 55°.

In the second and third inventions, a vibration-damping material isdisposed in the range noted above with regard to the first invention,and with regard to the second and third invention a vibration-dampingmaterial sheet having a vertical-direction length of about 110 mm toabout 150 mm is disposed between the inner bias layer and the outer biaslayer, with the above-noted position as the vertical-direction rear endregard. In this case, it is preferable to use a polyester-based resincomposition made of a polyester-based resin into which an at least oneof an electrically conductive material and a filler has been dispersedare prepared as the vibration-damping material sheet. The above-notedpolyester-based resin composition efficiently absorbs vibration energyand has a superior vibration-damping effect. As the above-notedpolyester-based resin, it is possible to use a polyester-based resinhaving a dicarboxylic acid component and diol component as unitcomponents. As the above-noted electrically conductive material, it ispossible to use as inorganic materials, for example, silver, iron, lead,copper, a copper alloy, nickel, a low melting point metal powder ormetal fiber; copper or silver microparticles covered with a preciousmetal; microparticles or whiskers of a metal oxide such as tin oxide,zinc oxide, or indium oxide; electrically conductive carbon powders,such as various types of carbon black or carbon nanotubes; and carbonfibers such as PAN carbon fibers, pitch-based carbon fibers, andvapor-phase grown graphite and the like. Organic materials that can beused are anti-static agents of the low polymer surfactant type; highpolymer anti-static agents; electrically conductive polymers such aspolypyrrole and polyanyline; and polymer microparticles that have beencovered by a metal. As the filler mentioned above, it is possible touse, for example, mica flakes, glass pieces, sericite, graphite, talc,aluminum flakes, boron nitride, molybdenum sulfide, and flake-typefillers such as scalelike filler.

As the vibration-damping material forming the vibration-damping materialsheet, it is possible to preferably use materials disclosed in theJapanese Patent Application Publication No. 2006-52377 and JapanesePatent Application Publication No. 2008-189854, which are incorporatedby reference, and more specifically, it is preferable to use Neofade(product name) made by Mitsubishi Gas Chemical Company, Inc.

The layer made of the inner bias layer, the outer bias layer, and thevibration-damping material layer may be formed by laminating the innerbias layer prepreg sheet and the outer bias layer prepreg sheet with thevibration-damping material layer sheet interposed therebetween, andwinding the laminate of the inner bias layer prepreg sheet and the outerbias layer prepreg sheet around a metal core. That is, whereas it isusual to use as the vibration-damping material sheet a sheet made of apolyester resin composition that does not have pressure-sensitiveadhesion, even in the case as noted above, in which the inner bias layerprepreg sheet and the outer bias layer prepreg sheet, in between whichis sandwiched the vibration-damping material sheet, are wound around themetal core, by sandwiching the vibration-damping material sheet betweenthe inner bias layer and the outer bias layer, even if a sheet withoutpressure-sensitive adhesion is used as the vibration-damping sheet, itis possible to prevent peeling away of the vibration-damping materialsheet.

It is preferable that the vibration-damping material sheet be disposedas the position of the beginning part of the winding of the inner biaslayer prepreg sheet and the outer bias layer prepreg sheet around themetal core. By doing this, because the vibration-damping material sheetis sandwiched between the inner bias layer and the outer bias layer, itis possible to minimize the reduction in the performance of the shafteven if there is insufficient holding between the fiber-reinforced resinlayers and the vibration-damping material sheet.

Additionally, in the case of winding a laminate of the inner bias layerprepreg sheet and the outer bias layer prepreg sheet with thevibration-damping material sheet sandwiched therebetween around a metalcore as noted above, it is appropriate to wind the vibration-dampingmaterial sheet one turn around the metal core and wind the laminate ofthe inner bias layer prepreg sheet and the outer bias layer prepregsheet around the metal core four to six turns. By doing this, thevibration-damping material sheet is wound close to the metal core,surface unevenness of the shaft surface is reduced and, because thevibration-damping material sheet is surrounded by and sandwiched betweenthe inner bias layer prepreg sheet and the outer bias layer prepregsheet, it is difficult for the position of the vibration-dampingmaterial sheet to shift at the time of molding, and it is possible toachieve the effect of it being difficult for the vibration-dampingmaterial sheet to peel away during use.

In the present invention, in the case of using a layer made by the innerbias layer, the outer bias layer, and the vibration-damping materiallayer as the inner layer of the shaft, if necessary a straight layerhaving a fiber direction that coincides with the shaft axial directionor a hoop layer having a fiber direction that is perpendicular to theshaft axial direction or the like may be formed on the outside of theouter bias layer. Additionally, painting may be done to the outermostlayer of the shaft.

The shaft for a golf club and golf club using same according to thepresent invention achieves the following effects. Firstly, by virtue ofthe vibration-attenuating action of the vibration-damping materialsheet, the vibration of the shaft at the time of impact is reduced andthe vibration attenuates quickly, so that the feel of impact isimproved. Secondly, because of the low rigidity in the part in which thevibration-damping material sheet is disposed, flexure occurs easily inthe location in which the vibration-damping material sheet is disposed,and the overall shaft flexes, making the shaft easy to swing andstabilizing the ball that is struck.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic front elevation view showing one embodiment of ashaft for a golf club according to the present invention.

FIG. 2 is a schematic enlarged cross-sectional view along the line A-Aof FIG. 1.

FIG. 3 is a view showing the size of an example of a vibration-dampingshaft.

FIGS. 4 (a) and 4 (b) are views showing an example of a process formanufacturing the shaft for a golf club of FIG. 1.

FIGS. 5 (a) and 5 (b) are graphs showing the vibration-attenuatingeffect of the shaft for a golf club of FIG. 1.

FIG. 6 is a graph showing the rigidity distribution of the shaft for agolf club of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Although embodiments of the present invention are described below, withreference made to the accompanying drawings, the present invention isnot limited to these embodiments. FIG. 1 is a conceptual front elevationshowing an embodiment of a shaft for a golf club according to thepresent invention, and FIG. 2 is a conceptual enlarged cross-sectionalview along the line A-A of FIG. 1, the example shown being a men'sdriver.

The golf club shaft 10 of this example had, as fiber-reinforced resinlayers in sequence from the inside, an inner bias layer 12 having afiber direction that was inclined with respect to the shaft axialdirection, an outer bias layer 14 having a fiber direction that wasinclined with respect to the shaft axial direction in a directionopposite from that of the inner bias layer 12, and a straight layer 16having a fiber direction that coincides with the shaft axial direction.Each of the fiber-reinforced resin layers 12, 14, and 16 was formed bywinding a single prepreg sheet in the form of a sheet made byimpregnating a carbon fiber (roving) that had been aligned in parallelwith an epoxy resin or an unsaturated polyester resin from four to sixtimes around a metal core. However, the inner bias layer 12 and theouter bias layer 14 were formed by winding after laminating the prepregsheets that form same beforehand.

In the golf club shaft 10 of this example, with the end position regionof the attachment location of the grip 18 taken as thevertical-direction rear end 20, a vibration-damping material sheet layer22 having a vertical-direction height a of about 130 mm and made of apolyester-based resin composition (Neofade (product name) made byMitsubishi Gas Chemical Company, Inc.) of a polyester-based resin intowhich at least one of an electrically conductive material and a fillerhad been dispersed was interposed between the inner bias layer 12 andthe outer bias layer 14. The location of this vibration-damping materialsheet layer 22 was a position range from 64.1% to 75.2% of the shaftlength b from the shaft tip end (i.e., shaft end on the head side), andthe position of the vertical-direction rear end 20 of thevibration-damping material sheet layer 22 was a position that was about257 mm (distance d) from the shaft butt end (i.e., shaft end on the gripside). The above-noted 64.1% was the value of the leading end positionof the vibration-damping material sheet layer 22 (calculated by theformula (c-a)/b×100), and the 7.52% was the value of the rear endposition of the vibration-damping material sheet layer 22 (calculated bythe formula c/b×100). The vibration-damping material sheet layer 22 wasformed by one winding of a vibration-damping material one time around ametal core. The vibration-damping material sheet was, as shown in FIG.3, an equal-foot trapezoidal shape, the long side of which was about 130mm, the short side of which was about 30 mm, the width of which wasabout 40 mm, and the thickness of which was 0.145 mm.

The above example was that of a men's driver, and the locations ofdisposition of the vibration-damping sheet layer in this shift and othershafts were as shown below in Table 1.

TABLE 1 Overall shaft length Vibration-damping sheet (mm) layerdisposition location Shafts for a men's club For a wood club 1170Location 750 to 880 mm from the end For a utility club 1065 Location 610to 740 mm from the end For an iron club 990 Location 580 to 710 mm fromthe end Shafts for a women's club For a driver 1145 Location 720 to 850mm from the end For a fairway wood 1080 Location 660 to 790 mm from theend For a utility club 985 Location from 590 to 720 mm from the end Foran iron club 935 Location from 530 to 660 mm from the end

The golf club shaft of this example could, for example, be manufacturedby the sheet-winding method, using the following prepreg sheets.

(1) As shown in FIG. 4( a), a inner bias layer prepreg sheet 34 having afiber direction 30 that was at an inclination of 45° with respect to theshaft axial direction 32, an outer bias layer prepreg sheet 36 having afiber direction 30 that was at an inclination of 45° with respect to theshaft axial direction in the opposite direction from the inner biaslayer prepreg sheet 34, a straight layer prepreg sheet 38 having a fiberdirection 30 that coincides with the shaft axial direction 32, andvibration-damping material sheet 40 made of a polyester-based resincomposition made of a polyester-based resin into which at least one ofan electrically conductive material and a filler had been dispersed wereprepared.

(2) As shown in FIG. 4( b), the inner bias layer prepreg sheet 34 andthe outer bias layer prepreg sheet 36 were laminated with thevibration-damping material sheet 40 interposed therebetween. In thiscase, the vibration-damping material sheet 40 was disposed at thebeginning part of winding around the metal core 42.

(3) After winding the inner bias layer prepreg sheet 34 and the outerbias layer prepreg sheet 36 around the metal core 42, the straight layerprepreg sheet 38 was wound around the outside thereof, and tape wasfurther wound around the outside thereof.

(4) The prepreg sheets were thermally cured in a high-temperature oven.

(5) After forming the shaft, the metal core and tape were removed, andthe outer peripheral surface of the straight layer was made smooth byfiling, after which the outer peripheral surface of the straight layerwas painted.

FIG. 5 shows the vibration characteristics of the golf club shaft ofFIG. 1. FIG. 5( a) shows the vibration of the shaft after it was used tomanufacture a golf club, measured by an accelerometer, with the clubsuspended vertically and a hammer used to strike the head at anoff-center location. The off-center location was a location about 20 mmdistant in the toe direction from the center of the face surface. FromFIG. 5( a), it could be seen that the shaft of this example, providedwith a vibration-damping material sheet layer, not only had smallvibration of the shaft at the time of impact, but also exhibits fastattenuation of vibration.

FIG. 6 shows the rigidity distribution of the golf club shaft of FIG. 1.From FIG. 6, it could be seen that the shaft of this example, providedwith a vibration-damping material sheet layer, had a lower rigidity atthe location of the vibration-damping material sheet, about 750 to about880 mm from the shaft end, than one in which a vibration-dampingmaterial sheet layer was not disposed, so that the entire shaft flexesand the struck ball is stabilized.

1. A golf club shaft comprising: resin layers, the resin layerscomprising: an inner bias fiber-reinforced resin layer with reinforcingfibers aligned along the first direction that is inclined with respectto the shaft axial direction; an outer bias fiber-reinforced resin layerthe second direction that is inclined with respect to the shaft axialdirection opposite to the first direction; and a vibration-dampingmaterial sheet layer having a vertical-direction length of about 110 mmto about 150 mm, being interposed between the inner bias layer and theouter bias layer and being positioned at a range from about 55% to about80% of the shaft length from a shaft tip.
 2. A golf club shaft accordingto claim 1, wherein the vibration damping material sheet layer is apolyester-based resin composition made of a polyester-based resin intowhich at least one of an electrically conductive material and a fillerhas been dispersed.
 3. A golf club shaft according to claim 1, whereinthe layer made of the inner bias layer, the outer bias layer, and thevibration-damping material sheet layer is formed by laminating the innerbias layer prepreg sheet and the outer bias layer prepreg sheet with thevibration-damping material sheet interposed therebetween, and windingthe laminate of the inner bias layer prepreg sheet and the outer biaslayer prepreg sheet around a metal core.
 4. A golf club shaft accordingto claim 3, wherein the vibration-damping material sheet is disposed ata position of the beginning part of the winding of the inner bias layerprepreg sheet and the outer bias layer prepreg sheet around the metalcore.
 5. A golf club shaft according to claim 3, wherein thevibration-damping material sheet is wound one turn around the metalcore, and the laminate of the inner bias layer prepreg sheet and theouter bias layer prepreg sheet is wound four to six turns around themetal core.
 6. A golf club using a golf club shaft comprising aplurality of resin layers as the plurality of resin layers comprising aninner bias fiber-reinforced resin layer with reinforcing fibers alignedalong the first direction that is inclined with respect to the shaftaxial direction; an outer bias fiber-reinforced resin layer the seconddirection is that inclined with respect to the shaft axial directionopposite to the first direction; and a vibration-damping material sheetlayer having a vertical length of about 110 mm to about 150 mm, beinginterposed between the inner bias layer and the outer bias layer, andbeing positioned from about 235 mm to about 270 mm from a butt end ofthe shaft taken as the rear end in the vertical direction.
 7. A golfclub using a golf club shaft comprising: resin layers, the resin layerscomprising: an inner bias fiber-reinforced resin layer with reinforcingfibers aligned along the first direction that is inclined with respectto the shaft axial direction; an outer bias fiber-reinforced resin layerwith reinforcing fibers aligned along the second direction that isinclined with respect to the shaft axial direction opposite to the firstdirection; and a vibration-damping material sheet layer having avertical length of about 110 mm to about 150 mm, being interposedbetween the inner bias layer and the outer bias layer, and beingpositioned at a region of a position of the end of the grip attachmentlocation is taken as the rear end in the vertical direction.
 8. A golfclub according to claim 6, wherein the vibration-damping material sheetlayer is a polyester-based resin composition made of a polyester-basedresin into which at least one of an electrically conductive material anda filler has been dispersed.
 9. A golf club according to claim 6,wherein the layer made of the inner bias layer, the outer bias layer,and the vibration-damping material layer is formed by laminating theinner bias layer prepreg sheet and the outer bias layer prepreg sheetwith the vibration-damping material layer sheet interposed therebetween,and winding the laminate of the inner bias layer prepreg sheet and theouter bias layer prepreg sheet around a metal core.
 10. A golf clubaccording to claim 9, wherein the vibration-damping material sheet isdisposed at a position of the beginning part of the winding of the innerbias layer prepreg sheet and the outer bias layer prepreg sheet aroundthe metal core.
 11. A golf club according to claim 9, wherein thevibration-damping material sheet is wound one turn around the metalcore, and the laminate of the inner bias layer prepreg sheet and theouter bias layer prepreg sheet is wound four to six turns around themetal core.